The present invention relates to microelectronic device assemblies, and more specifically to inhibiting or preventing fluctuations in a reference voltage applied to a microelectronic die.
Microelectronic devices are generally complex, delicate components used in larger products. A typical microelectronic device includes a microelectronic die, a support structure attached to the die, and a protective casing encapsulating the die. The microelectronic die can be a semiconductor device (e.g., a microprocessor or a memory device), a field emission display, or another type of device. The support structure is generally a lead frame having a plurality of leads, or an interposing substrate having electrically conductive traces and solder ball pads. The protective casing is generally a hard plastic, such as a thermosetting material, that is molded around the die. The protective casing encapsulates the die and a portion of the support structure to protect the die from environmental hazards and physical shocks.
The microelectronic dies include integrated circuitry and a plurality of bond-pads that are coupled to the integrated circuitry. In a typical application for a DRAM memory device, a die will have a reference voltage (Vref) bond-pad, a plurality of supply voltage (Vdd) and ground voltage (Vss) bond-pads, a plurality of signal bond-pads (e.g., clock lines, address lines, and data lines), a column address strobe ({overscore (CAS)}) bond-pad, and a row address strobe ({overscore (RAS)}) pad. The bond-pads are often arranged in a fine pitch array on one side of the die, and each bond-pad is coupled to the appropriate voltage source or signal source. For example, the Vref bond-pad is coupled to a reference voltage source, the Vss and Vdd bond-pads are coupled to appropriate electrical potentials, and the signal bond-pads are coupled to the correct signal sources. The support structures are accordingly configured so that the leads or traces couple the bond-pads on the die to the corresponding voltage and signal sources.
The current trend in microchip fabrication is to manufacture smaller and faster microelectronic dies for computers, cell phones and many other products. As the dies become smaller, the bond-pads on the dies are also smaller and spaced closer together. Additionally, as the microelectronic dies become faster and have a larger capacity, the components of the integrated circuitry are much smaller and spaced closer together so that more components can be fabricated in the dies. Many dies accordingly have a limited amount of real estate for the integrated circuitry and the bond-pads. As a result, the Vref bond-pad may be adjacent to a signal bond-pad for a data or clock signal such that the wire-bond lines between these bond-pads are immediately adjacent to one another.
One drawback of locating the Vref bond-pad adjacent to a signal bond-pad is that the reference voltage may fluctuate because of coupled noise. This drawback is particularly problematic in high-frequency dies with clock speeds of over 100 MHz and signal frequencies of over 200 MHz. Such fluctuations in the reference voltage at the Vref bond-pad can cause the microelectronic die to malfunction because it is critical to maintain a constant reference voltage. Therefore, it would be desirable to prevent fluctuations in the reference voltage at the Vref bond-pad in microelectronic dies that have the Vref bond-pad in the proximity of a signal bond-pad.
The present invention is directed toward microelectronic devices and methods for manufacturing such microelectronic devices. One aspect of the invention is directed toward a microelectronic device having a microelectronic die and a support structure for coupling the die to voltage sources and signal sources. The microelectronic die can have integrated circuitry and a plurality of bond-pads coupled to the integrated circuitry. The bond-pads, for example, can include a reference voltage (Vref) bond-pad and a signal bond-pad adjacent to the Vref bond-pad. The signal bond-pad can be for a clock signal, a data signal, a strobe signal, an address signal, or another type signal for operating the integrated circuitry.
The support structure can be a lead frame or an interposing substrate having a plurality of conductive members coupled to the bond-pads of the die. The conductive members can accordingly be metal leads in the case of lead frames or traces connected to solder ball-pads in the case of interposing substrates. Each conductive member can have a first end with a bond-site proximate to a corresponding bond-pad of the die, a second end defining an external connector, and an elongated conductive section connecting the bond-site to the external connector. The conductive members are generally arranged so that at least some of the bond-sites are arranged in a first row in which the bond-sites and a portion of the elongated sections are spaced apart from one other by a first gap width. The support structure can more specifically include a first conductive member having a first bond-site coupled to the Vref bond-pad by a first wire-bond line and a second conductive member having a second bond-site coupled to the signal bond-pad by a second wire-bond line. The first bond-site of the first conductive member can be spaced apart from the second bond-site of the second conductive member by a second gap width greater than the first gap width.
In one particular embodiment of a microelectronic device, the support structure includes a first conductive member, a second conductive member, and a third conductive member. The first conductive member has a first elongated section and a first bond-site coupled to the Vref bond-pad by a first wire-bond line, and the second conductive member has a second elongated section and a second bond-site coupled to the signal bond-pad by a second wire-bond line. The third conductive member has a shielding section adjacent to and between the first and second bond-sites of the first and second conductive members. The shielding section of the third conductive member can also extend between a portion of the first and second elongated sections of the first and second conductive members. The third conductive member of this particular embodiment can be coupled to an electrical potential, such as the ground voltage, to establish an electrical shield that inhibits or even prevents electrical interference between a high-frequency input/output signal applied to the second conductive member and the reference voltage applied to the first conductive member.